Why do planets orbit the sun in a similar plane?

Question

Why aren't they orbiting in random planes (but obviously at discrete distances from the sun, otherwise they would collide)? I would have expected the solar system to look like (how text books describe) electrons orbiting a nucleus. The same question applies to galaxies - why do they form spiral discs?

Answer 1

Conservation of angular momentum and gas dissipation.

The solar system condensed from interstellar material. That condensation involved a huge change (factor of about a million) in size. The original interstellar material had a small amount of angular momentum. That angular momentum is (approximately) conserved during the condensation to a protostellar nebula. Therefore, what was spinning slowly, in a disorganized way, in the interstellar cloud winds up spinning quickly, in a much more organized way, in the very much smaller protostellar nebula. Gas motions parallel to the angular momentum vector (that is, perpendicular to the plane of the ecliptic) tend to damp because of energy losses in shocks. Circular gas motions in the plane of the disk tend to persist, because those gas streamlines do not intersect with each other. The result is a solar-system-sized disk of dense gas, with the proto-sun in the middle, and most of the gas in circular orbits in the plane of the ecliptic. All the planets form from this disk, and all therefore share the net motions of the gas streamlines in that disk.

The process is similar for the disks of disk galaxies. Note that in galaxies, it is only the gaseous disks that wind up in a plane. Any stars that form previous to the formation of the disk are in a more spherical distribution.

P.S. The planetoids, asteroids, and meteorids that wind up in funny orbits get there duing a period of chaos after the formation of the planets. The orbits of the planets are not stable when they first form, and big chunks of protoplanetary matter interact, both gravitationally and physically. During this period, a collision between two planet-sized chunks made the Earth and Moon as we known them.

Answer 2

Though the Sun appears to be stationary, just like the earth, it is spinning on its axis too. The planes on which all the planets exist are almost perpendicular to this sun's axis with centrifugal forces being at work. The plane is not exactly the same for all planets though. Each planet's plane varies by a small degree. Ditto for galaxies. Again, the spiral galaxies seem to spin around their centers (somewhat similar to a hurricane).

Answer 3

Possibly because all the planets coalesced from the same mass of material when the solar system formed. Other objects which seem to have been sucked into the solar system afterwards, like comets, and Pluto, orbit in different planes.

Answer 4

I don't know about this, but I love your question, so I hope someone who does know will answer, because I want to know for sure, too.

I suspect that the planets orbit in a plain that is in line with the sun's equator, and I suspect that the moon orbits the Earth in the same way. At least that would explain the disc phenomenon.

Answer 5

The solar system was formed by small objects and interstellar gases comming together. When the smaller particles were attracted to each other as the solar system was forming they began to spin about each other. Like marbles shot toward a bowling ball on a bed. Unless directed exactly at the center of bowling ball they tend to orbit it. More and more particles joined in (coalesced) and collided (adding lots of heat) the entire mass was spining about a common center. Its a little more complicated than this. Check out this link for more detailed info http://en.wikipedia.org/wiki/Solar_system#Formation

Answer 6

Certain objects, some larger than Pluto, do not orbit the Sun in the Plane of the Elliptic.

Answer 7

Because in both cases, the material accreted as flat discs to the central gravity well, along the equatorial axis of the gravity well (the equatorial bulge of a celestial body is what causes this).

You can observe the phenomenon in process with Saturn, where the orbiting particles are a disc, in their current state prior to accumulating into a proto-moon or moons. (which they will eventually, although Saturn's rings are famously stable.)

Answer 8

Plane = Plane ts = Planets.

Answer 9

due to the Sun's gravity force

Answer 10

BMI baby